Foam and laminate, and use thereof

Abstract

To provide a foam that exhibits excellent foam performance while having superior recyclability.SOLUTION: A foam comprises at least one α-olefin copolymer (A) selected from the group consisting of a copolymer of ethylene and α-olefin (A1) and a copolymer of propylene and α-olefin (A2) meeting specific requirements, or a composition containing the α-olefin copolymer (A), wherein the composition has a gel fraction of 0 mass% or more and 30 mass% or less as measured by 140°C xylene extraction in accordance with JIS K 6796.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to foams and laminates and uses thereof, and more particularly to foams and laminates containing an α-olefin copolymer and uses thereof. [Background technology]

[0002] Crosslinked foams, which have a low specific gravity, i.e., are lightweight and flexible, and have high mechanical strength, have been widely used for interior and exterior building materials, interior materials, automobile parts such as door glass runs, packaging materials, daily necessities, etc. Foams obtained by simply foaming a resin to reduce weight have low mechanical strength, so it is a known technique to prevent the decrease in mechanical strength by further bonding molecular chains within the foam through a crosslinking reaction of the resin.

[0003] Crosslinked resin foams are also used in footwear or footwear parts, such as the soles (mainly midsoles) of sports shoes, etc. This is because footwear or footwear parts must be lightweight, resist deformation over long periods of use, and have the mechanical strength and impact resilience to withstand severe conditions of use.

[0004] It is widely known that cross-linked foams of ethylene-vinyl acetate copolymer have been used for shoe soles. However, cross-linked foams molded using this ethylene-vinyl acetate copolymer composition have a high specific gravity and a large compression set. Therefore, when used for shoe soles, for example, they are heavy, and with long-term use, the soles become compressed, causing a loss of mechanical strength such as rebound resilience.

[0005] On the other hand, crosslinked foams made from ethylene-α-olefin copolymers have high mechanical strength, light weight, and flexibility, and are therefore used in building exterior and interior materials, automotive parts such as door glass runs, packaging materials, and daily necessities, as well as in footwear and footwear parts, such as the soles (mainly midsoles) of sports shoes. In this regard, Patent Documents 1 and 2 describe inventions relating to crosslinked foams made from ethylene-α-olefin copolymers and crosslinked foams made from a blend of ethylene-vinyl acetate copolymer and ethylene-α-olefin copolymer, respectively. However, although these inventions achieve improved low specific gravity and compression set, they do not achieve sufficient performance.

[0006] Patent Document 3 describes an ethylene-α-olefin-non-conjugated polyene random copolymer that meets certain requirements, and a composition containing the copolymer and a vulcanizing agent such as an organic peroxide. Patent Document 3 also describes that when the composition further contains a blowing agent such as a nitroso compound, an azo compound, or an azide compound, a vulcanized foam can be obtained by heating and foaming the composition. However, the invention described in Patent Document 3 still leaves room for improvement in terms of providing a foam of uniform quality with a low specific gravity and small compression set.

[0007] Various attempts have been made to obtain foams with low specific gravity and low compression set. For example, Patent Document 4 discloses a foam that can be used for footwear and footwear parts, which is obtained by crosslinking and foaming a composition containing an ethylene-α-olefin copolymer, a small amount of an ethylene-α-olefin-non-conjugated polyene copolymer, azodicarbonamide (ADCA), and a crosslinking agent. Patent Document 4 also discloses that, despite its low specific gravity, this foam has a smaller compression set than foams obtained from a composition that does not contain an ethylene-α-olefin-non-conjugated polyene copolymer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 9-501447 [Patent Document 2] Japanese Patent Application Publication No. 11-206406 [Patent Document 3] Japanese Patent Application Publication No. 11-5818 [Patent Document 4] International Publication No. 2007 / 132731 Pamphlet Summary of the Invention [Problem to be solved by the invention]

[0009] Crosslinked foams, such as those made of ethylene-vinyl acetate copolymers, are often produced by crosslinking and foaming plastics such as ethylene-vinyl acetate copolymers in the presence of azodicarbonamide (ADCA) and a crosslinking agent. However, such crosslinked foams generally lose their fluidity, making them difficult to recycle by melting and remolding. Therefore, an object of the present invention is to provide a foam that has excellent foam performance and is also excellent in recyclability. [Means for solving the problem]

[0010] As a result of intensive research into solving the above problems, the present inventors have found that the above problems can be solved by physically foaming a specific α-olefin polymer, and have thus completed the present invention. The present invention relates to the following [1] to

[14] . [1] one or more α-olefin copolymers (A) selected from the group consisting of ethylene-α-olefin copolymers (A1) and propylene-α-olefin copolymers (A2) satisfying the following requirement (A2-a): A composition containing the α-olefin copolymer (A) It consists of A foam having a gel fraction of 0 to 30% by mass as determined by xylene extraction at 140°C of the composition in accordance with JIS K6796: (A2-a) Contains 60 to 95 mol % of structural units derived from propylene and 5 to 40 mol % of structural units derived from an α-olefin having 2 to 20 carbon atoms (excluding propylene) (wherein the total amount of the structural units derived from propylene and the structural units derived from the α-olefin is 100 mol %). [2] The foam according to [1], wherein the α-olefin copolymer (A) satisfies the following requirements (Aa) and (Ab): (Aa) Density 0.850-0.910g / cm 3 in the range of; (Ab) The melt flow rate measured at 230°C under a load of 2.16 kg according to the method of ASTM D1238 is in the range of 0.01 to 200 g / 10 min. [3] The foam according to [1] or [2], wherein the α-olefin copolymer (A) is the ethylene-α-olefin copolymer (A1). [4] The foam according to [3], wherein the ethylene-α-olefin copolymer (A1) is an ethylene-1-butene copolymer. [5] The composition containing the α-olefin copolymer (A) is 70 parts by mass or more and less than 100 parts by mass of the α-olefin copolymer (A); A propylene polymer (B) that satisfies the requirement (Ba) is more than 0 parts by mass and 30 parts by mass or less (where the total amount of the α-olefin copolymer (A) and the propylene polymer (B) is 100 parts by mass). The foam according to [1] or [2], which is a composition comprising: (Ba) Contains more than 95 mol % and not more than 100 mol % of structural units derived from propylene and 0 mol % or more and less than 5 mol % of structural units derived from an α-olefin having 2 to 20 carbon atoms (excluding propylene) (where the total amount of the structural units derived from propylene and the structural units derived from the α-olefin is taken as 100 mol %). [6] The foam according to [5], wherein the α-olefin copolymer (A) is the propylene-α-olefin copolymer (A2). [7] The foam according to [6], wherein the propylene-α-olefin copolymer (A2) is a propylene-ethylene-1-butene copolymer, and the propylene-based polymer (B) is a propylene homopolymer. [8] A laminate comprising a layer made of the foam according to any one of [1] to [7] and a layer made of one or more materials selected from the group consisting of polyolefin, polyurethane, rubber, leather and artificial leather. [9] Footwear comprising the foam according to any one of [1] to [7] or the laminate according to [8].

[10] A footwear part comprising the foam according to any one of [1] to [7] or the laminate according to [8].

[11] The footwear part according to

[10] , which is a midsole, an inner sole or a sole.

[12] one or more α-olefin copolymers (A) selected from the group consisting of ethylene-α-olefin copolymers (A1) and propylene-α-olefin copolymers (A2) satisfying the following requirement (A2-a): A composition containing the α-olefin copolymer (A) A method for producing a foam, comprising the step of physically foaming a (A2-a) Contains 60 to 95 mol % of structural units derived from propylene and 5 to 40 mol % of structural units derived from an α-olefin having 2 to 20 carbon atoms (excluding propylene) (wherein the total amount of the structural units derived from propylene and the structural units derived from the α-olefin is 100 mol %).

[13] The composition containing the α-olefin copolymer (A) is 70 parts by mass or more and less than 100 parts by mass of the α-olefin copolymer (A); A propylene polymer (B) that satisfies the requirement (Ba) is more than 0 parts by mass and 30 parts by mass or less (where the total amount of the α-olefin copolymer (A) and the propylene polymer (B) is 100 parts by mass). The method for producing a composition according to

[12] , (B-a) More than 95 mol% and 100 mol% or less of the structural units derived from propylene, and 0 mol% or more and less than 5 mol% of the structural units derived from α-olefins having 2 to 20 carbon atoms (excluding propylene) (however, the total amount of the structural units derived from propylene and the structural units derived from α-olefins is 100 mol%).

[14] The step of physically foaming includes The production method according to

[12] or

[13] , which includes a step of impregnating with a supercritical fluid. [Advantages of the Invention]

[0011] According to the present invention, it is possible to provide a foam having excellent recyclability while having excellent foam performance. [Embodiments for Carrying Out the Invention]

[0012] Hereinafter, the present invention will be specifically described. Here, in this specification, "~" indicating a numerical range means "M or more and N or less" when expressed as, for example, "M~N" (M and N are numerical values satisfying M < N), unless otherwise specified.

[0013] Also, in this specification, when an olefin constituting a certain polymer is M, the expression "structural unit derived from M" may be used, which means "structural unit corresponding to M", that is, a structural unit having a pair of bonds formed by opening the π bond constituting the double bond of M. For example, "structural unit derived from ethylene" means a structural unit represented by -CH2-CH2-, "structural unit derived from propylene" means a structural unit represented by -CH2-CH(-CH3)-, and "structural unit derived from α-olefin" specifically means a structural unit represented by -CH2-CRR' - (R and R' are each independently a hydrogen atom or an alkyl group).

[0014] [Foam] The foam of the present invention is one or more α-olefin copolymers (A) selected from the group consisting of ethylene-α-olefin copolymers (A1) and propylene-α-olefin copolymers (A2) satisfying the following requirement (A2-a): A composition containing the α-olefin copolymer (A) Consists of: (A2-a) Contains 60 to 95 mol % of structural units derived from propylene and 5 to 40 mol % of structural units derived from an α-olefin having 2 to 20 carbon atoms (excluding propylene) (wherein the total amount of the structural units derived from propylene and the structural units derived from the α-olefin is 100 mol %).

[0015] The foam of the present invention has a gel fraction of 0 to 30% by mass when the composition is extracted with xylene at 140°C according to JIS K 6796. This gel fraction is a value measured as the proportion of the content insoluble in xylene at 140°C relative to the entire foam.

[0016] In the prior art, resin foams for applications requiring high mechanical strength, such as footwear or footwear components, are often obtained by crosslinking the resin to bond molecular chains within the foam, thereby ensuring a certain level of foam performance, such as impact resilience. Such crosslinked foams tend to have a high gel fraction due to the crosslinking of the resin, resulting in a loss of fluidity and making it difficult to recycle by melting and remolding the foam. On the other hand, the present invention, from the perspective of recyclability, employs a specific copolymer as the α-olefin copolymer (A), enabling foams with sufficient mechanical strength to be obtained without the use of a crosslinking agent, or by minimizing the amount of crosslinking agent used. It is believed that such foams have a low gel fraction. Therefore, in the present invention, to distinguish them from crosslinked foams, the gel fraction of the foam is specified to be within a certain range. The gel fraction is preferably 0 to 10% by mass, more preferably 0 to 5% by mass. The gel fraction can be measured using the method described in the Examples.

[0017] The foam of the present invention preferably has a specific gravity of 0.10 to 0.30. When the specific gravity is within the above range, the foam can be made lighter while still ensuring sufficient strength. The foam of the present invention preferably has an Asker C hardness of 20 to 80. The Asker C hardness can be measured according to the "Spring Hardness Test Type C Test Method" described in JIS K 7312:1996, Appendix 2. When the Asker C hardness is within the above range, the foam can exhibit good cushioning properties and strength when used in footwear.

[0018] The foam of the present invention preferably has a rebound resilience of 30 to 75%. The rebound resilience can be measured in accordance with JIS K 6255:2013. When the rebound resilience is within the above range, the foam can exhibit good rebound properties when used in footwear. The expansion ratio of the foam of the present invention is preferably 3 to 10. When the expansion ratio is within the above range, the foam can be made lighter while still ensuring sufficient strength.

[0019] <α-olefin copolymer (A)> The α-olefin copolymer (A) constituting the foam of the present invention is at least one selected from the group consisting of ethylene-α-olefin copolymers (A1) and propylene-α-olefin copolymers (A2) satisfying the following requirement (A2-a):

[0020] Ethylene-α-olefin copolymer (A1) One example of the α-olefin copolymer (A) constituting the foam of the present invention is an ethylene-α-olefin copolymer (A1). That is, the ethylene-α-olefin copolymer (A1) is a copolymer consisting of structural units derived from ethylene and structural units derived from an α-olefin. The ethylene and α-olefin may be, for example, fossil fuel-derived monomers or biomass-derived monomers, and these monomers may be used alone or in combination of two or more.

[0021] The α-olefin constituting the ethylene-α-olefin copolymer (A1) is typically an α-olefin having 3 or more carbon atoms, preferably an α-olefin having 3 to 20 carbon atoms. Specific examples include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-hexadecene, 1-octadecene, 1-nonadecene, 1-eicosene, and 4-methyl-1-pentene. Among these, α-olefins having 3 to 10 carbon atoms are preferred, with propylene, 1-butene, 1-hexene, and 1-octene being particularly preferred. In one particularly preferred and exemplary embodiment of the present invention, the α-olefin is 1-butene. These α-olefins may be used singly or in combination.

[0022] The ethylene-α-olefin copolymer (A1) preferably contains 75 to 95 mol %, and more preferably 80 to 94 mol %, of structural units derived from ethylene, and 5 to 25 mol %, and more preferably 6 to 20 mol %, of structural units derived from an α-olefin having 3 to 20 carbon atoms, where the total amount of ethylene and α-olefin is 100 mol %.

[0023] Propylene-α-olefin copolymer (A2) Another example of the α-olefin copolymer (A) constituting the foam of the present invention is a propylene-α-olefin copolymer (A2), which is a copolymer consisting of structural units derived from propylene and structural units derived from an α-olefin. The propylene-α-olefin copolymer (A2) satisfies the following requirement (A2-a): (A2-a) Contains 60 to 95 mol % of structural units derived from propylene and 5 to 40 mol % of structural units derived from an α-olefin having 2 to 20 carbon atoms (excluding propylene) (wherein the total amount of the structural units derived from propylene and the structural units derived from the α-olefin is 100 mol %).

[0024] The ethylene and α-olefin may be, for example, a fossil fuel-derived monomer or a biomass-derived monomer, and these monomers may be used alone or in combination of two or more. Specific examples of the α-olefin constituting the propylene-α-olefin copolymer (A2) include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-hexadecene, 1-octadecene, 1-nonadecene, 1-eicosene, and 4-methyl-1-pentene. Among these, α-olefins having 2 or 4 to 10 carbon atoms are preferred, with ethylene, 1-butene, 1-hexene, and 1-octene being particularly preferred. In one particularly preferred exemplary embodiment of the present invention, the α-olefin is a combination of ethylene and 1-butene. These α-olefins may be used alone or in combination of two or more.

[0025] As described above, the propylene-α-olefin copolymer (A2) contains 60 to 95 mol % of structural units derived from propylene and 5 to 40 mol % of structural units derived from an α-olefin having 2 to 20 carbon atoms (excluding propylene). The amount of structural units derived from propylene is preferably 65 to 85 mol %. On the other hand, the amount of structural units derived from an α-olefin having 2 to 20 carbon atoms (excluding propylene) is preferably 15 to 35 mol %. Here, the total amount of propylene and α-olefin is 100 mol %. The α-olefins constituting the propylene-α-olefin copolymer (A2) may be one type alone or a combination of two or more types. When the propylene-α-olefin copolymer (A2) contains two or more types of α-olefins, the total amount of the two or more types of α-olefins falls within the numerical range shown above for "the amount of structural units derived from an α-olefin having 2 to 20 carbon atoms (excluding propylene)."

[0026] α-olefin copolymer (A) The α-olefin copolymer (A) constituting the foam of the present invention may be the above-mentioned ethylene-α-olefin copolymer (A1) or the above-mentioned propylene-α-olefin copolymer (A2).The α-olefin copolymer (A) may also be a combination of the above-mentioned ethylene-α-olefin copolymer (A1) and the above-mentioned propylene-α-olefin copolymer (A2). In one preferred exemplary embodiment of the present invention, the α-olefin copolymer (A) is the above-mentioned ethylene-α-olefin copolymer (A1). In this case, the ethylene-α-olefin copolymer (A1) is particularly preferably an ethylene-1-butene copolymer.

[0027] In another preferred exemplary embodiment of the present invention, the α-olefin copolymer (A) is the above-mentioned propylene-α-olefin copolymer (A2). In this case, the propylene-α-olefin copolymer (A2) is particularly preferably a propylene-ethylene-1-butene copolymer. In either case, the α-olefin copolymer (A) preferably satisfies the following requirements (Aa) and (Ab).

[0028] (Aa) Density 0.850-0.910g / cm 3 is in the range. The α-olefin copolymer (A) used in the present invention usually has a density of 0.850 g / cm 3 or more, preferably 0.855 g / cm 3 More preferably, 0.857 g / cm 3 More preferably, 0.858 g / cm 3 or more, usually 0.910 g / cm 3 or less, preferably 0.909 g / cm 3 or less, more preferably 0.908 g / cm 3 or less, more preferably 0.907 g / cm 3The density of the ethylene-α-olefin copolymer (A) is a value measured at 23°C according to ASTM D1505. When the density satisfies this range, the resulting foam is preferably excellent in balance between flexibility and strength, and between rigidity and impact strength.

[0029] (Ab) Melt flow rate (MFR) measured at 230°C under a load of 2.16 kg according to the method of ASTM D1238 2.16 ) is in the range of 0.01 to 200 g / 10 min. The ethylene-α-olefin copolymer (A) used in the present invention has an MFR 2.16 The melt flow rate (measured at 230°C under a load of 2.16 kg according to the method of ASTM D1238) is preferably in the range of 0.01 to 200 g / 10 min.

[0030] The MFR of the α-olefin copolymer (A) used in the present invention can be appropriately selected, preferably within this range, depending on the intended use. 2.16 is not particularly limited, but is usually 0.01 g / 10 min or more, preferably 0.08 g / 10 min or more, more preferably 0.05 g / 10 min or more, even more preferably 0.1 g / 10 min or more, particularly preferably 0.2 g / 10 min or more, and is usually 200 g / 10 min or less, preferably 100 g / 10 min or less, more preferably 40 g / 10 min or less, even more preferably 25 g / 10 min or less, particularly preferably 10 g / 10 min or less. 2.16 tends to be smaller.

[0031] MFR 2.16 It is preferable that the MFR is equal to or less than the upper limit in that the strength of the obtained molded article is improved. 2.16 is equal to or greater than the above lower limit, in that the flowability of the α-olefin copolymer (A) during melt molding is improved.

[0032] The α-olefin copolymer (A) satisfying the above requirements (Aa) and (Ab) may be in the form of a thermoplastic elastomer or a thermoplastic resin.

[0033] <Method for producing α-olefin copolymer (A)> The method for producing the ethylene-α-olefin copolymer (A1), which can be the ethylene-α-olefin copolymer (A), is not particularly limited. For example, the ethylene-α-olefin copolymer (A1) can be suitably produced by copolymerizing ethylene and at least one α-olefin in the presence of an olefin polymerization catalyst. The method for producing the propylene-α-olefin copolymer (A2), which can be the ethylene-α-olefin copolymer (A), is not particularly limited, and can be suitably produced, for example, by copolymerizing propylene with at least one α-olefin having 2 to 20 carbon atoms (excluding propylene) in the presence of an olefin polymerization catalyst.

[0034] The olefin polymerization catalyst that can be used in the production of the ethylene-α-olefin copolymer (A1) and the propylene-α-olefin copolymer (A2) is not particularly limited as long as the object of the present invention is achieved, and may be a known olefin polymerization catalyst such as a metallocene catalyst. Examples of such olefin polymerization catalysts include olefin polymerization catalysts comprising the following catalyst components [A] and [B]: [A] Bridged metallocene compound. [B] (b-1) organoaluminum oxy compound, (b-2) a compound that reacts with the bridged metallocene compound [A] to form an ion pair, and (b-3) At least one compound selected from the group consisting of organoaluminum compounds. The copolymerization can be carried out, for example, in the presence of such an olefin polymerization catalyst by solution polymerization of ethylene and one or more α-olefins in the case of producing the ethylene-α-olefin copolymer (A1), or by solution polymerization of propylene and one or more α-olefins having 2 to 20 carbon atoms (excluding propylene) in the case of producing the propylene-α-olefin copolymer (A2), at a temperature of 0 to 200°C in the presence of a solvent. However, the α-olefin copolymer (A) used in the present invention is not limited to the above-mentioned production method as long as it satisfies the above-mentioned properties. For example, a metallocene compound other than a crosslinked metallocene compound may be used in the copolymerization, a co-catalyst other than the catalyst component [B] may be used, or the α-olefin copolymer (A) may be prepared by a technique such as reactor blending or physical blending using two or more known types of ethylene copolymers or propylene copolymers. The temperature and pressure at which the copolymerization is carried out can be appropriately adjusted according to the desired physical properties.

[0035] In order to suppress variations in physical properties, the ethylene-α-olefin copolymer (A) obtained by the polymerization reaction and other components added as desired are preferably melted by any method and then kneaded, granulated, or the like.

[0036] <Propylene polymer (B)> The foam of the present invention may contain, in addition to the α-olefin copolymer (A), a propylene-based polymer (B) satisfying the following requirement (Ba): (Ba) Contains more than 95 mol % and not more than 100 mol % of structural units derived from propylene and 0 mol % or more and less than 5 mol % of structural units derived from an α-olefin having 2 to 20 carbon atoms (excluding propylene) (where the total amount of the structural units derived from propylene and the structural units derived from the α-olefin is taken as 100 mol %).

[0037] In this case, the foam of the present invention is formed from a composition containing the ethylene-α-olefin copolymer (A) and the propylene polymer (B). The α-olefin constituting the propylene polymer (B) is the same as the α-olefin described above in the section "Propylene-α-olefin copolymer (A2)" above, and specific examples include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-hexadecene, 1-octadecene, 1-nonadecene, 1-eicosene, and 4-methyl-1-pentene. Among these, α-olefins having 2 or 4 to 10 carbon atoms are preferred, and ethylene, 1-butene, 1-hexene, and 1-octene are particularly preferred. These α-olefins may be used alone or in combination.

[0038] However, the difference between the propylene polymer (B) usable in the present invention and the propylene-α-olefin copolymer (A2) is the content of structural units derived from α-olefins. That is, the propylene polymer (B) is either a propylene homopolymer or a propylene-α-olefin copolymer having a lower content of structural units derived from α-olefins than the propylene-α-olefin copolymer (A2). In one particularly preferred exemplary embodiment of the present invention, the propylene polymer (B) is a propylene homopolymer. In addition, the propylene polymer (B) has an MFR 2.16 is preferably 0.1 g / 10 min or more, more preferably 0.3 g / 10 min or more, even more preferably 0.5 g / 10 min or more, and is preferably 50 g / 10 min or less, more preferably 20 g / 10 min or less, even more preferably 10 g / 10 min or less.

[0039] The method for producing the propylene polymer (B) is not particularly limited, but it can be suitably produced, for example, by homopolymerizing propylene or copolymerizing propylene with at least one of the above-mentioned α-olefins in the presence of an olefin polymerization catalyst. The olefin polymerization catalyst that can be used in producing the propylene polymer (B) is not particularly limited as long as the object of the present invention is achieved, and may be a known olefin polymerization catalyst such as a metallocene catalyst. Here, the temperature and pressure at which the homopolymerization or polymerization is carried out can be appropriately adjusted according to the desired physical properties.

[0040] In the foam of the present invention, the propylene polymer (B) is an optional component. In one preferred exemplary embodiment of the present invention, the foam of the present invention contains the α-olefin copolymer (A) but does not contain the propylene polymer (B). In particular, when the α-olefin copolymer (A) is the ethylene-α-olefin copolymer (A1), the foam of the present invention preferably does not contain the propylene polymer (B). In another preferred exemplary embodiment of the present invention, the foam of the present invention contains the propylene polymer (B) in addition to the α-olefin copolymer (A). In particular, when the α-olefin copolymer (A) is the propylene-α-olefin copolymer (A2), the foam of the present invention preferably contains the propylene polymer (B). In this case, the foam of the present invention contains the propylene polymer (B), which has the advantages of suppressing stickiness and providing an excellent balance between flexibility and strength.

[0041] When the foam of the present invention is formed from a composition containing the α-olefin copolymer (A) and the propylene polymer (B), i.e., when the foam of the present invention consists of a composition containing the α-olefin copolymer (A) and the propylene polymer (B), the composition contains the α-olefin copolymer (A) and the propylene polymer (B) in proportions of 70 to less than 100 parts by mass, preferably 75 to 96 parts by mass, of (A) and more than 0 to 30 parts by mass, preferably 4 to 25 parts by mass (where the total of the α-olefin copolymer (A) and the propylene polymer (B) is 100 parts by mass).

[0042] That is, in the foam of the present invention, the mass ratio ((A) / (B)) of the α-olefin copolymer (A) to the propylene polymer (B) is 100 / 0 to 70 / 30, with 100 / 0 being one preferred embodiment. On the other hand, when the foam of the present invention contains the propylene polymer (B), the mass ratio ((A) / (B)) is desirably in the range of 96 / 4 to 75 / 25.

[0043] <Other polymer components> When the foam of the present invention is formed from a composition containing the α-olefin copolymer (A) and the propylene polymer (B), the composition may optionally contain other polymer components (hereinafter referred to as "other polymer components") that do not fall under either the α-olefin copolymer (A) or the propylene polymer (B). Examples of other polymer components include, but are not limited to, ethylene-vinyl acetate copolymers and ethylene-α-olefin-non-conjugated polyene copolymers. When the composition of the present invention contains polymer components other than the α-olefin copolymer (A) and the propylene polymer (B), the content of such polymer components is typically 50 parts by mass or less, preferably about 1 to 30 parts by mass, per 100 parts by mass of the total of (A) and (B).

[0044] In this specification, the α-olefin copolymer (A), the optional propylene polymer (B), and the optional other polymer components may be collectively referred to as the “polymer components.”

[0045] <Physical foaming agent (C)> The foam of the present invention may consist solely of a polymer component such as the α-olefin copolymer (A). The foam of the present invention is generally obtained by foaming a polymer component such as the ethylene-α-olefin copolymer (A), and this foaming is often carried out using a blowing agent. Therefore, the polymer component such as the α-olefin copolymer (A) that provides the foam of the present invention is often used in the form of a composition containing the polymer component such as the α-olefin copolymer (A) and a blowing agent.

[0046] The composition contains dicumyl peroxide (DCP), di-t-butyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3, 1,3-bis(t-butylperoxyisopropyl)benzene, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(t-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, t-butyl peroxybenzoate, t-butyl perbenzoate, and t-butyl The composition may further contain a crosslinking agent such as an organic peroxide, such as peroxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, or t-butylcumyl peroxide. Alternatively, in addition to the crosslinking agent, the composition may further contain a peroxy crosslinking aid, such as sulfur, p-quinone dioxime, p,p'-dibenzoylquinone dioxime, N-methyl-N-4-dinitrosoaniline, nitrosobenzene, diphenyl guanidine, or trimethylolpropane-N,N'-m-phenylenedimaleimide; or a crosslinking aid, such as divinylbenzene, triallyl cyanurate (TAC), or triallyl isocyanurate (TAIC). However, in the present invention, since it is preferable to sufficiently reduce the gel fraction when the foam is formed, it is preferable that the composition does not contain a crosslinking agent or crosslinking aid, and even if it does contain one, it is preferable that the amount of either is kept to a minimum.

[0047] When the composition contains the crosslinking agent, the content of the crosslinking agent is usually 0.01 to 0.30 parts by mass, preferably 0.01 to 0.10 parts by mass, per 100 parts by mass of the total of the α-olefin copolymer (A), the optional propylene polymer (B), and the optional other polymer components (i.e., 100 parts by mass of all polymer components). When the composition contains the crosslinking agent and the crosslinking aid, the crosslinking aid is desirably used in an amount such that the mass ratio of the crosslinking aid to the crosslinking agent [crosslinking aid / crosslinking agent] is 1 / 30 to 5 / 1, preferably 1 / 20 to 3 / 1, more preferably 1 / 15 to 2 / 1, and particularly preferably 1 / 10 to 1 / 1.

[0048] In the present invention, a physical foaming agent (C) can be used as the foaming agent. The physical foaming agent (C) is a substance that generates bubbles in a polymer component such as the α-olefin copolymer (A) by utilizing the temperature- and / or pressure-dependent change in solubility in the polymer component, and does not necessarily involve a chemical reaction during foaming.

[0049] Examples of the physical blowing agent (C) include organic physical blowing agents such as various aliphatic hydrocarbons such as methanol, ethanol, propane, butane, pentane, and hexane; various chlorinated hydrocarbons such as dichloroethane, dichloromethane, and carbon tetrachloride; and various fluorochlorohydrocarbons such as chlorofluorocarbons, as well as inorganic physical blowing agents such as air, carbon dioxide, nitrogen, argon, and water. Among these, carbon dioxide, nitrogen, and argon are excellent because they do not need to be converted into steam, are inexpensive, and have very little risk of environmental pollution and ignition, and of these, nitrogen and carbon dioxide are particularly excellent.

[0050] The physical blowing agent (C) can often be used in the form of a gas. However, the physical blowing agent (C) may be used in the form of a supercritical fluid to sufficiently increase its solubility in polymer components such as the α-olefin copolymer (A). In a preferred exemplary embodiment of the present invention, the physical blowing agent (C) is used in the form of a supercritical fluid. Carbon dioxide has a critical pressure of 7.38 MPa and a critical temperature of 31.1°C, making it relatively easy to convert it into a supercritical fluid. Nitrogen has a critical pressure of 3.4 MPa and a critical temperature of -147.1°C, and is a supercritical fluid at room temperature.

[0051] In the present invention, a physical blowing agent (C) is used as the blowing agent, and therefore no decomposition residue of the blowing agent remains in the resulting foam. This prevents mold contamination during crosslinking and foaming of the composition. Moreover, since the physical blowing agent is not powdery, it has excellent kneadability. Furthermore, the use of this physical blowing agent prevents the resulting foam from having an unpleasant odor (such as the ammonia odor generated during the decomposition of azodicarbonamide (ADCA)).

[0052] As a method of storing the physical blowing agent (C), in the case of small-scale production, carbon dioxide, nitrogen, etc. can be used in a cylinder and supplied to the injection molding machine, extrusion molding machine, etc. through a pressure reducing valve, or the pressure can be increased by a pump or the like and supplied to the injection molding machine, extrusion molding machine, etc.

[0053] In addition, in facilities for manufacturing foamed products on a large scale, storage tanks for liquefied carbon dioxide, liquefied nitrogen, etc. are installed, and the liquefied carbon dioxide, liquefied nitrogen, etc. are vaporized through a heat exchanger, and then supplied to injection molding machines, extrusion molding machines, etc. through piping and pressure reducing valves.

[0054] When a liquid physical blowing agent is used as the physical blowing agent (C), the storage pressure is preferably in the range of 0.13 to 100 MPa. When the physical foaming agent (C) is used, the amount of the physical foaming agent (C) added is determined appropriately depending on the desired expansion ratio, and is usually 0.1 to 15 parts by mass, and preferably 0.5 to 10 parts by mass, per 100 parts by mass of the total of the α-olefin copolymer (A), the optional propylene polymer (B), and the optional other polymer components.

[0055] On the other hand, in relation to the physical foaming agent (C), in the prior art, chemical foaming agents (C') are often used as foaming agents when producing plastic foams. These chemical foaming agents (C') are chemical substances that generate gas by thermal decomposition or other chemical reactions. Specific examples of chemical foaming agents (C') include: Azodicarbonamide (ADCA), 1,1'-azobis(1-acetoxy-1-phenylethane), dimethyl-2,2'-azobisbutyrate, Dimethyl-2,2'-azobisisobutyrate, 2,2'-azobis(2,4,4-trimethylpentane), 1,1'-azobis(cyclohexane-1-carbonitrile), azo compounds such as 2,2'-azobis[N-(2-carboxyethyl)-2-methyl-propionamidine]; Nitroso compounds such as N,N'-dinitrosopentamethylenetetramine (DPT); 4,4'-oxybis(benzenesulfonylhydrazide), hydrazine derivatives such as diphenylsulfone-3,3'-disulfonylhydrazide; Semicarbazide compounds such as p-toluenesulfonylsemicarbazide; Organic thermal decomposition type blowing agents such as trihydrazinotriazine, Bicarbonates such as sodium hydrogen carbonate and ammonium hydrogen carbonate, carbonates such as sodium carbonate and ammonium carbonate; nitrites such as ammonium nitrite, Examples of inorganic thermal decomposition type blowing agents include hydrogen compounds. Of these, azodicarbonamide (ADCA) tends to be used frequently because of the large amount of gas it generates during thermal decomposition.

[0056] When a chemical foaming agent (C') is used as the foaming agent, a foaming assistant may be used in combination with the chemical foaming agent (C'). The foaming assistant acts to lower the decomposition temperature of the chemical foaming agent (C'), promote decomposition, and homogenize the bubbles. Examples of such foaming assistants include zinc oxide (ZnO), zinc stearate, organic acids such as salicylic acid, phthalic acid, stearic acid, and oxalic acid, and urea or its derivatives.

[0057] However, when a foam is produced using azodicarbonamide (ADCA) or the like as a blowing agent, the resulting foam may emit an odor (off-odor) derived from the blowing agent, such as the ammonia odor generated upon decomposition of ADCA. The presence of such an odor (off-odor) is undesirable for use in footwear and footwear components. Furthermore, when ADCA or the like is used as a blowing agent, problems such as discoloration may occur in the resulting foam, which is undesirable from the viewpoint of aesthetics, etc. Therefore, in the present invention, a chemical blowing agent (C') is not typically used.

[0058] <Other ingredients> The foam of the present invention may optionally contain components other than the above-described components, such as various additives such as fillers, heat stabilizers, weather stabilizers, flame retardants, hydrochloric acid absorbers, and pigments. Examples of the various additives include those known to be added to general olefin-based resins. These may be included in the foam of the present invention to the extent that they do not impair the object of the present invention.

[0059] [Method of manufacturing foam] The foam of the present invention can be produced by any method without particular limitation, but can be prepared, for example, by the following method.

[0060] The foam of the present invention can be obtained, for example, by a production method including a step of physically foaming the α-olefin copolymer (A) or a composition containing the α-olefin copolymer (A). The physical foaming step may be carried out by first impregnating the α-olefin copolymer (A) or a composition containing the α-olefin copolymer (A) in the gaseous state of the physical foaming agent (C) under pressure, and then releasing the pressure. Alternatively, the physical foaming step may be carried out by impregnating the α-olefin copolymer (A) or a composition containing the α-olefin copolymer (A) in a supercritical fluid.

[0061] When a supercritical fluid is used as the physical foaming agent (C), the physical foaming step can be carried out, for example, by a step (SC1) of impregnating the α-olefin copolymer (A) or a composition containing the α-olefin copolymer (A) in a supercritical fluid; and a step (SC2) of injecting the mixture obtained in the step (SC1) into a mold, depressurizing it to foam it, and cooling and solidifying it in the mold; In this embodiment, the foam of the present invention is obtained in the form of an injected foam. The temperature and pressure for carrying out step (SC1) are not particularly limited as long as the physical foaming agent (C) is in a supercritical fluid state, but may be, for example, 100 to 300°C and 100 to 300 bar (i.e., 10 to 30 MPa). On the other hand, the temperature and pressure for carrying out step (SC2) are set lower than those for carrying out step (SC1), for example, 1 to 50 bar (i.e., 0.1 to 5.0 MPa). The mold temperature for carrying out step (SC2) is, for example, 5 to 60°C.

[0062] Here, before the physical foaming step, the α-olefin copolymer (A) or a composition containing the α-olefin copolymer (A) may be melt-plasticized in advance using a kneader such as a Banbury mixer, a roll (a roll mill such as a two-roll mill or a three-roll mill), an extruder, etc. Alternatively, the α-olefin copolymer (A) or a composition containing the α-olefin copolymer (A) may be charged into an injection molding machine, and the melt-plasticizing step and the subsequent physical foaming step may be carried out together in the injection molding machine.

[0063] When the foam of the present invention is formed from a composition containing the α-olefin copolymer (A), the composition containing the α-olefin copolymer (A) can be obtained by mixing the α-olefin copolymer (A) and, if necessary, the propylene-based polymer (B) and / or the other polymer components by an appropriate method such as a Henschel mixer.

[0064] The foam obtained by physically foaming the above-mentioned α-olefin copolymer (A) or a composition containing the above-mentioned α-olefin copolymer (A) is preferably used for the laminates, footwear, or footwear parts described later.

[0065] [Laminate] The laminate of the present invention is a laminate having a layer made of the foam of the present invention described above and a layer made of at least one material selected from the group consisting of polyolefin, polyurethane, rubber, leather, and artificial leather.

[0066] The polyolefin, polyurethane, rubber, leather, and artificial leather are not particularly limited, and conventionally known polyolefins, polyurethanes, rubbers, leathers, and artificial leathers can be used. Such laminates are particularly suitable for use in footwear and footwear parts.

[0067] [Footwear and footwear parts] The footwear and footwear components of the present invention are both made using the foam or laminate of the present invention. That is, it can be said that the footwear and footwear components of the present invention both include the foam or laminate of the present invention. Examples of footwear components include shoe soles, shoe midsoles, inner soles, soles, sandals, etc.

[0068] The footwear or footwear component of the present invention uses the foam or laminate of the present invention, and is therefore lightweight and can be prevented from deforming over long periods of use. [Example]

[0069] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring various physical properties described in the examples are as follows.

[0070] [Evaluation of polymer properties] ·MFR The MFR (melt flow rate, g / 10 min) was measured in accordance with ASTM D1238 at 190°C under a load of 2.16 kg or 10 kg, or at 230°C under a load of 2.16 kg. ·density Density of copolymer (kg / m 3 ) was measured at 23°C in accordance with ASTM D1505. ·composition The ethylene, propylene, and 1-butene contents of each copolymer were determined under the following conditions: 13 C-NMR measurements were performed, and the values ​​were calculated by analyzing the obtained spectra. Equipment: Bruker BioSpin AVANCE III cryo-500 nuclear magnetic resonance spectrometer Measurement nuclei: 13 C(125MHz) Measurement mode: Single pulse proton broadband decoupling Pulse width: 45° (5.00 μsec) Number of points: 64k Measurement range: 250 ppm (-55 to 195 ppm) Repeat time: 5.5 seconds Number of times accumulated: 128 Measurement solvent: orthodichlorobenzene / benzene-d6 (4 / 1 [v / v]) Sample concentration: ca. 60 mg / 0.6 mL Measurement temperature: 120℃ Window function: exponential (BF: 1.0 Hz) Chemical shift reference: δδ signal (29.73 ppm)

[0071] [Raw materials used] Ethylene-α-olefin copolymer (A1) The copolymers used as the ethylene-α-olefin copolymer (A1) in the following examples are as follows: Ethylene-α-olefin copolymer (A1-1): ethylene-1-butene copolymer (ethylene content = 89 mol%, 1-butene content = 11 mol%, MFR (230 °C, 2.16 kg) = 33 g / 10 min, density 885 kg / m 3 ) Ethylene-α-olefin copolymer (A1-2): ethylene-1-butene copolymer (ethylene content = 89 mol%, 1-butene content = 11 mol%, MFR (230 °C, 2.16 kg) = 6.7 g / 10 min, density 885 kg / m 3 ) Ethylene-α-olefin copolymer (A1-3): ethylene-1-butene copolymer (ethylene content = 89 mol%, 1-butene content = 11 mol%, MFR (230 °C, 2.16 kg) = 2.2 g / 10 min, density 885 kg / m 3 ) Ethylene-α-olefin copolymer (A1-4): Ethylene-1-butene copolymer (ethylene content = 92 mol%, 1-butene content = 8 mol%, MFR (230 °C, 2.16 kg) = 2.2 g / 10 min, density 905 kg / m 3 ) Ethylene-α-olefin copolymer (A1-5): Ethylene-1-butene copolymer (ethylene content = 89 mol%, 1-butene content = 11 mol%, MFR (230 °C, 2.16 kg) = 1.1 g / 10 min, MFR (190 °C, 2.16 kg) (I2) = 0.5 g / 10 min, MFR (190 °C, 10 kg) (I10) = 4.2, density 885 kg / m 3 )

[0072] Propylene-α-olefin copolymer (A2) The polymers used as the propylene-α-olefin copolymer (A2) in the following examples are as follows: Propylene-α-olefin copolymer (A2-1): A propylene-ethylene-1-butene copolymer having the following properties, produced in the same manner as described in the examples of WO 2004 / 87775. Ethylene content = 16 mol%, 1-butene content = 6 mol%, Melt flow rate (MFR) (230°C, 2.16 kg) = 6 g / 10 min, Melting point (Tm) = 50 ° C. Isotactic triad fraction (mm) = 92%, Molecular weight distribution (Mw / Mn)=2.0

[0073] Propylene polymer (B) The polymers used as the propylene polymer (B) in the following examples are as follows: Propylene polymer (B-1): Homopolypropylene (Prime Polymer Co., Ltd., Prime Polypro F107, MFR (230°C, 2.16 kg) = 7 g / 10 min, melting point = 163°C)

[0074] Other polymers (C) The polymers used as other polymers (C) in the following comparative examples are as follows: Ethylene-vinyl acetate copolymer (C-1): Evaflex EV360, manufactured by Mitsui Dow Polychemicals Co., Ltd., VA content = 25% by mass, MFR (190°C, 2.16 kg load) = 2 g / 10 min

[0075] [Example 1] (Preparation of foam) 100 parts by mass of ethylene-α-olefin copolymer (A1-1) was placed into an injection molding machine equipped with a Trexel Inc. supercritical fluid (SCF) metering and supply system, "MuCell T-200," via a hopper. After heating and plasticizing in the cylinder, the mixture was impregnated with 1.08 g of supercritical nitrogen and injected at a speed of 66 mm / s into a mold (counter pressure 15 bar) measuring 200 mm in length, 10 mm in width, and 20 mm in thickness. The mixture was then cooled for 10 minutes to obtain a foam. The cylinder and mold temperatures were as shown in Table 1.

[0076] (Measurement of foam properties) The foam obtained in the above "Preparation of foam" was subjected to measurements of the following physical properties. The results are shown in Table 1 below. Gel fraction The gel content was measured according to JIS K6796. Specifically, approximately 0.3 g of a test piece was placed in a wire mesh with a #325 (43 μm) mesh and immersed in a solvent (xylene) in an amount sufficient to keep the test piece immersed at 140°C for 3 hours. The mass of the sample was measured before and after immersion in the solvent, and the gel fraction was calculated using the following formula. G = 100 × (m2 / m1) G: Gel fraction (%) m1: Mass of the test piece before immersion in the solvent (mg) m2: Mass of residue after solvent immersion (mg) ·specific gravity The specific gravity of the foam was measured in accordance with JIS K 7222:2005. The samples used for measuring the specific gravity were taken from a location 20 mm or more inward from each of the four sides of the foam with the largest area and 2.5 mm or more inward from the surface of the foam. Samples were prepared from five locations on the foam, and the specific gravity was measured and the average was used. Asker C hardness The Asker C hardness was measured in a 23°C environment according to the "Spring Hardness Test Type C Test Method" described in Appendix 2 of JIS K 7312:1996. Rebound elasticity The impact resilience was measured in accordance with JIS K 6255: 2013. The sample was prepared by cutting the foam into a cylindrical shape with a diameter of 30 mm and a thickness of 15 mm or more, and cutting off one of the two parallel flat surfaces of the cylinder to make it 10 mm thick. The measurement was carried out in an atmosphere of 23°C.

[0077] [Example 2] A foam was produced and its physical properties were measured in the same manner as in Example 1, except that the ethylene-α-olefin copolymer (A1-1) was changed to the ethylene-α-olefin copolymer (A1-2).

[0078] [Example 3] A foam was produced and its physical properties were measured in the same manner as in Example 1, except that the ethylene-α-olefin copolymer (A1-1) was changed to the ethylene-α-olefin copolymer (A1-3).

[0079] [Example 4] A foam was produced and its physical properties were measured in the same manner as in Example 1, except that the ethylene-α-olefin copolymer (A1-1) was changed to the ethylene-α-olefin copolymer (A1-4).

[0080] [Example 5] A foam was produced and its physical properties were measured in the same manner as in Example 1, except that the ethylene-α-olefin copolymer (A1-1) was changed to the ethylene-α-olefin copolymer (A1-5).

[0081] [Example 6] A foam was prepared and its physical properties were measured in the same manner as in Example 1, except that the ethylene-α-olefin copolymer (A1-1) was changed to a mixture of 90 parts by mass of propylene-α-olefin copolymer (A2-1) and 10 parts by mass of propylene-based polymer (B-1). The composition, foaming conditions and physical properties of the foams obtained in each example are shown in Table 1 below.

[0082] [Table 1]

[0083] [Comparative Example 1] A mixture consisting of 100 parts by weight of ethylene vinyl acetate copolymer (C-1), 3.0 parts by weight of zinc oxide, 1.0 part by weight of stearic acid, 3.0 parts by weight of titanium oxide, 0.1 parts by weight of triallyl isocyanurate (TAIC) (trade name: M-60 [TAIC content: 60% by weight], manufactured by Nippon Kasei Chemical Co., Ltd.), 0.7 parts by weight of dicumyl peroxide (DCP), and 1.3 parts by weight of azodicarbonamide (ADCA) was kneaded with a roll at a roll surface temperature of 120°C for 10 minutes and then formed into a sheet to obtain a sheet-like composition. The obtained resin composition sheet was filled into a press mold (mold size: length 140 mm, width 65 mm, thickness 10 mm) and pressurized with 180 kgf / cm. 2 A crosslinked foam was obtained by applying pressure and heating for 15 minutes under conditions of 170° C. The physical properties of the obtained crosslinked foam were measured in the same manner as in Example 1.

[0084] Comparative Example 2 A crosslinked foam was produced and its physical properties were measured in the same manner as in Comparative Example 1, except that the amount of DCP was changed to 0.9 parts by mass and the amount of ADCA was changed to 1.5 parts by mass. The compositions and physical properties of the crosslinked foams obtained in the respective comparative examples are shown in Table 2 below.

[0085] [Table 2]

Claims

1. one or more α-olefin copolymers (A) selected from the group consisting of ethylene / α-olefin copolymers (A1) and propylene / α-olefin copolymers (A2) satisfying the following requirement (A2-a): A composition containing the α-olefin copolymer (A) It consists of A foam having a gel fraction of 0 to 30% by mass as determined by xylene extraction at 140°C according to JIS K6796: (A2-a) Contains 60 to 95 mol % of structural units derived from propylene and 5 to 40 mol % of structural units derived from an α-olefin (excluding propylene) having 2 to 20 carbon atoms (provided that the total amount of the structural units derived from propylene and the structural units derived from the α-olefin is 100 mol %).

2. The foam according to claim 1, wherein the α-olefin copolymer (A) satisfies the following requirements (A-a) and (A-b): (A-a) Density is 0.850 to 0.910 g / cm ３ in the range of (Ab) The melt flow rate measured at 230° C. under a load of 2.16 kg according to the method of ASTM D1238 is in the range of 0.01 to 200 g / 10 min.

3. 2. The foam according to claim 1, wherein the α-olefin copolymer (A) is the ethylene / α-olefin copolymer (A1).

4. 4. The foam according to claim 3, wherein the ethylene / α-olefin copolymer (A1) is an ethylene / 1-butene copolymer.

5. The composition containing the α-olefin copolymer (A) is 70 parts by mass or more and less than 100 parts by mass of the α-olefin copolymer (A); a propylene polymer (B) satisfying requirement (Ba-a) of more than 0 parts by mass and not more than 30 parts by mass (where the total amount of the α-olefin copolymer (A) and the propylene polymer (B) is 100 parts by mass); 2. The foam of claim 1, wherein the foam is a composition comprising: (Ba-a) Contains more than 95 mol% and 100 mol% or less of structural units derived from propylene and 0 mol% or more and less than 5 mol% of structural units derived from an α-olefin (excluding propylene) having 2 to 20 carbon atoms (provided that the total amount of the structural units derived from propylene and the structural units derived from the α-olefin is 100 mol%).

6. 6. The foam according to claim 5, wherein the α-olefin copolymer (A) is the propylene / α-olefin copolymer (A2).

7. 7. The foam according to claim 6, wherein the propylene-α-olefin copolymer (A2) is a propylene-ethylene-1-butene copolymer, and the propylene-based polymer (B) is a propylene homopolymer.

8. A laminate comprising a layer made of the foam according to claim 1 and a layer made of one or more materials selected from the group consisting of polyolefin, polyurethane, rubber, leather and artificial leather.

9. Footwear comprising the foam of claim 1 or the laminate of claim 8.

10. A footwear component comprising the foam of claim 1 or the laminate of claim 8.

11. The footwear part according to claim 10, which is a midsole, an inner sole, or a sole.

12. one or more α-olefin copolymers (A) selected from the group consisting of ethylene / α-olefin copolymers (A1) and propylene / α-olefin copolymers (A2) satisfying the following requirement (A2-a): A composition containing the α-olefin copolymer (A) A method for producing a foam, comprising the step of physically foaming a (A2-a) Contains 60 to 95 mol % of structural units derived from propylene and 5 to 40 mol % of structural units derived from an α-olefin (excluding propylene) having 2 to 20 carbon atoms (provided that the total amount of the structural units derived from propylene and the structural units derived from the α-olefin is 100 mol %).

13. The composition containing the α-olefin copolymer (A) is 70 parts by mass or more and less than 100 parts by mass of the α-olefin copolymer (A); a propylene polymer (B) satisfying requirement (Ba-a) of more than 0 parts by mass and not more than 30 parts by mass (where the total amount of the α-olefin copolymer (A) and the propylene polymer (B) is 100 parts by mass); The method according to claim 12, wherein the composition comprises: (Ba-a) Contains more than 95 mol% and 100 mol% or less of structural units derived from propylene and 0 mol% or more and less than 5 mol% of structural units derived from an α-olefin (excluding propylene) having 2 to 20 carbon atoms (provided that the total amount of the structural units derived from propylene and the structural units derived from the α-olefin is 100 mol%).

14. The physical foaming step comprises: The method of claim 12, further comprising the step of impregnating with a supercritical fluid.

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